In simple electronic models, a resistor is considered perfect as is a capacitor and an inductor. In practice, they all are flawed and have small elements of each other in their behaviour. For example a simple inductor can be a coil of wire, but obviously a length of wire has resistance.
Impedance is the real-world aspect of a circuit made up of resistors, inductors and capacitors. It accounts for e.g. voltage and current not being always in phase. In domestic audio, the measurement is encountered most reliably when describing loudspeakers with passive crossovers.